DESCRIPTION

Extended attributes are
name:value
pairs associated with inodes (files, directories, symbolic links, etc.).
They are extensions to the normal attributes which are associated
with all inodes in the system (i.e., the
stat(2)
data).
A complete overview of extended attributes concepts can be found in
xattr(7).

listxattr()
retrieves the list
of extended attribute names associated with the given
path
in the filesystem.
The retrieved list is placed in
list,
a caller-allocated buffer whose size (in bytes) is specified in the argument
size.
The list is the set of (null-terminated) names, one after the other.
Names of extended attributes to which the calling process does not
have access may be omitted from the list.
The length of the attribute name
list
is returned.

llistxattr()
is identical to
listxattr(),
except in the case of a symbolic link, where the list of names of
extended attributes associated with the link itself is retrieved,
not the file that it refers to.

flistxattr()
is identical to
listxattr(),
only the open file referred to by
fd
(as returned by
open(2))
is interrogated in place of
path.

A single extended attribute
name
is a null-terminated string.
The name includes a namespace prefix; there may be several, disjoint
namespaces associated with an individual inode.

If
size
is specified as zero, these calls return the current size of the
list of extended attribute names (and leave
list
unchanged).
This can be used to determine the size of the buffer that
should be supplied in a subsequent call.
(But, bear in mind that there is a possibility that the
set of extended attributes may change between the two calls,
so that it is still necessary to check the return status
from the second call.)

Example

The
list
of names is returned as an unordered array of null-terminated character
strings (attribute names are separated by null bytes (aq\0aq)), like this:

RETURN VALUE

On success, a nonnegative number is returned indicating the size of the
extended attribute name list.
On failure, -1 is returned and
errno
is set appropriately.

ERRORS

E2BIG

The size of the list of extended attribute names is larger than the maximum
size allowed; the list cannot be retrieved.
This can happen on filesystems that support an unlimited number of
extended attributes per file such as XFS, for example.
See BUGS.

ENOTSUP

Extended attributes are not supported by the filesystem, or are disabled.

VERSIONS

These system calls have been available on Linux since kernel 2.4;
glibc support is provided since version 2.3.

CONFORMING TO

These system calls are Linux-specific.

BUGS

As noted in
xattr(7),
the VFS imposes a limit of 64 kB on the size of the extended
attribute name list returned by
listxattr(7).
If the total size of attribute names attached to a file exceeds this limit,
it is no longer possible to retrieve the list of attribute names.

EXAMPLE

The following program demonstrates the usage of
listxattr()
and
getxattr(2).
For the file whose pathname is provided as a command-line argument,
it lists all extended file attributes and their values.

To keep the code simple, the program assumes that attribute keys and
values are constant during the execution of the program.
A production program should expect and handle changes during
execution of the program.
For example,
the number of bytes required for attribute keys
might increase between the two calls to
listxattr().
An application could handle this possibility using
a loop that retries the call
(perhaps up to a predetermined maximum number of attempts)
with a larger buffer each time it fails with the error
ERANGE.
Calls to
getxattr(2)
could be handled similarly.

The following output was recorded by first creating a file, setting
some extended file attributes,
and then listing the attributes with the example program.

SEE ALSO

COLOPHON

This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.